Unsaturated polyester resin molding powder

ABSTRACT

AN UNSATURATED POLYESTER RESIN WHICH IS A SOLID CAPABLE OF BEING GROUND INTO A FREE FLOWING POWDER AT ROOM TEMPERATURE COMPRISES A MIXTURE OF AN X, B-ETHYLENICALLY UNSATURATED MONOMER AND A CONDENSATION POLYMER FORMED BY ESTERIFYING A DICARBOXYLIC ACID, AT LEAST A PORTION OF WHICH CONTAINS ETHYLENIC UNSATURATION, WITH A DIHYDRIC ALCOHOL WHEREIN AT LEAST A PORTION OF THE DIHYDRIC ALCOHOL COMPRISES 1,3-DI(2-HYDROXYETHOXY) BENZENE OR 1,4-DI(2HYDROXYETHOXY BENZENE.

Jan. 4, 1972 M. E. BAUM UNSATURATED POLYESTER RESIN MOLDING POWDER Filed May 8, 1970 wtDOI ON l tol OQONNIOQ Hq xmmhmml INVENTOR.

MEL V/N E. .f5/10M United States Patent O 3,632,667 UNSATURATED POLYESTER RESIN MOLDING POWDER Melvin E. Baum, Monroeville, Pa., assigner to Kappers Company, Inc. Continuation-in-part of abandoned application Ser. No. 700,311, Dec. 23, 1967. This application May 8, 1970, Ser. No. 35,738

Int. Cl. C08f 21/00, 21/02 U.S. Cl. 260-861 Claims ABSTRACT OF THE DISCLOSURE CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of applicants copending application Ser. No. 700,311, led Dec. 23, 1967 now abandoned.

BACKGROUND OF THE INVENTION Unsaturated polyester resins, which comprise a mixture of an ethylenically unsaturated copolymerizable monomer and a condensation polymer formed by polyesterifying dicarboxylic acids at least a portion of which contains ethylenic unsaturation with dihydric alcohols, can be cured to form thermosetting products which have uses in industry. These resins are particularly useful when glass fibers are dispersed therein as reinforcement. Pipes, panels and the like can be formed from such reinforced thermosetting resins. Although high molecular weight condensation polymers can be formed which are solids at room temperature, the addition of the copolymerizable monomer such as styrene to the polyester results in a liquid; the unsaturated monomer acting as a solvent for the condensation polymer. While it is possible to cross-link an unsaturated polyester molecule with another unsaturated polyester molecule, this is in reality seldom if ever done in commercial practice because of the cost diiference between the polyester and the monomer as well as the ease of copolymerizing the unsaturated condensation polymermonomer mixtures which have enhanced reactivity over the polyester alone. Therefore, the use of unsaturated polyester resins in certain applications such, as for example, in molding applications has been somewhat curtailed by the unavailability of the condensation polymer-monomer mixture as dry powders such as are available in other plastic resins such as phenolics or the like. As a result polyester resins have not been utilized in certain molding techniques and other techniques have had to be modified to allow the use of a liquid.

Quite surprisingly, it has now been discovered that a polyester resin can be formed which is a solid solution at room temperature and therefore, can be ground into a free flowing powder or pelletized or the like. Either 1,3- di(2hydroxyethoxy)benzene or 1,4-di(2-hydroxyethoxy) benzene is used in forming the initial condensation polymer or unsaturated polyester. The resulting unsaturated polyester can be dissolved While still hot in up to 50% by weight ethylenically unsaturated monomer and when cooled to room temperature, the result is a solid (yet uncured) polyester resin, a solid solution, which can be Patented Jan. 4, 1972 ice ground into a free-flowing powder or pelletized. The solid polyester resin solution can be used in molding applications, fluid bed coating techniques, or in impregnation of Iglass mats.

SUMMARY OF THE INVENTION In accordance with the invention, an unsaturated polyester resin which is a solid solution at room temperature comprises:

(a) 20 to 60% by total weight of monomer and polymer of an ,-ethylenically unsaturated monomer; and

(b) 40-80% by total weight of monomer and polymer of a condensation polymer formed by esterifying approximately stoichiometric amounts of (l) a dihydric alcohol at least 15 mole percent of which is selected from the class consisting of 1,3di(2hy droxyethoxy)benzene and 1,4 di(2 hydroxyethoxy) benzene; with (2) a dicarboxylic acid or anhydride at least a portion of which is an ethylenically unsaturated dicarboxylic acid or anhydride.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a ow sheet which depicts the process and product of the invention.

DETAILED DESCRIPTION Unsaturated polyester resins are well knownl in the art (see, for example, U.S. Pat. 2,255,313, issued to Carleton Ellis). The unsaturated polyester portion is a condensation polymer formed by polyesterifying dicarboxylic acids or anhydrides with dihydric alcohols. The term unsaturated polyester as used herein is defined as the condensation polymer produced by condensing dicarboxylic acid or its anhydride with the dihydric alcohol in approximately equimolar proportions and wherein at least a portion of which the dicarboxylic compound contains ethylenic unsaturation. The term unsaturated polyester resin as used herein is meant to dene the cornbination of (a) the condensation polymer or unsaturated polyester deiined above; and

(b) an ,-ethylenically unsaturated copolymerizable monomer such as styrene which can be copolymerized with the unsaturated polyester.

To provide unsaturation within the polyester, at least about 25 mole percent of the total dicarboxylic acids or anhydrides must contain ethylenic unsaturation. Examples of such unsaturated dicarboxylic acids include maleic, fumarie, itaconic, aconitic, mesaconic, citraconic, ethylmaleic and dichloromaleic acid. Also the anhydrides of these unsaturated dicarboxylic acids are contemplated by this invention. The remainder of` the dicarboxylic acids (up to about mole percent) may be a cyclic dicarboxylic acid or anhydride such as for example: phthalic acid or phthalic anhydride, tetrahydrophthalic acid, hexahydrophthalic acid, trans-1,4-cyclohexane dicarboxylic acid; 1,4- or 1,5- or 2,6- or 2,7-naphthalene dicarboxylic acid, and endo-cis bicyclo(2.2.l)-5-heptene2,3dicarboxylic acid. Other dicarboxylic acids suitable in the practice of the invention are straight chain saturated aliphatic dicarboxylic acids, such as for example, succinic acid, glutaric acid, adipic acid, and the like.

The dicarboxylic acids are polyesterilied with approximately equimolar amounts of dihydric alcohol. In accordance with the invention, at least l5 mole percent and preferably about 35 mole percent of the dihydric alcohol is 3 either l,3-di(2-hydroxyethoxy)benzene having the formula:

-O-CHz-CHz-OH or l,4-di(2-hydroxyethoxy)benzene having the formula:

(lyon2-Caron The remainder of the dihydric alcohols can be -any of the commonly used alkane diol's or oxy alkane diols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-butane diol, neopentyl glycol or the like as well as saturated cyclic dihydric alcohols such as 1,4-cyclohexane dimethanol, hydrogenated bis-phenol A or the like as well as mixtures of the foregoing.

The polyester is prepared by polyesterifying the ingredients as described above in accordance with the wellknown procedures for producing condensation resins such, as for example, described in the Carleton Ellis patent previously referred to. The polyesters may be produced by either the so-called fusion or the solvent process. Optionally present during the polycondensation or polyesterication are esterication catalysts such as tin chloride, zinc chloride, zinc acetate, nickel acetate or cadmium acetate. Also a `gelation inhibitor such as 'hydroquinone or para-tert-butyl-catechol may be added to the polycondensate. The gelation inhibitor inhibits premature polymerization of the unsaturated polyester with the cross linking monomer.

The molecular weight of the polyester is conveniently measured by the acid number of the polyester. This measurement is based on milliequivalents of KOH necessary to neutralize l gram of the polyester. For example, when the esterication is carried out by the so-called fusion process, the esterifioation is carried out under an inert blanket of gas such `as nitrogen in a temperature range of about l80220 C. for a period of 6-20 hours until an acid number below 100 and preferably below 50 is obtained. Esterication catalysts can be used as well as gelation inhibitors, such as are well knovm in the art.

While the foregoing has described the formation of the condensation polymer portion of the invention a's a single condensation, it is to be understood that the condensation polymer or polyester portion of the invention can also be formed by mixing together more than one polyester. For example, a polyester made by condensing l,3-di(2hy droxyethoxy)benzene with maleic anhydride in equirnolar proportions can not be hot blended with a second polyester made by condensing propylene glycol with maleic anhydride in equimolar proportions. However, regardless of the manner in which the polyester is formed, the resultant mixture must contain at least about l5 mole percent of the 1,3-di(2-hydroxyethoxy)benzene or l,4-di(2hydroxy ethoxy)benzene based on the total moles of dihydric alcohol used.

The hot liquid polyester or mixture of polyesters is then dissolved into an a,-ethylenically unsaturated monomer. The monomer acts both as a solvent for the polyester and as a subsequent copolymerization agent. Examples of such monomers include the vinyl type such as styrene, alphamethyl styrene, vinyl toluene, divinyl benzene, chlorostyrene, vinyl acetate, vinyl-2-chloroethyl ether, N-vinyl pyrrolidone, and Z-Vinyl pyridine.

- Also acrylic type cross linking monomers are suitable in the practice of the invention. Examples include methylmethacrylate, methylacrylate, acrylamide, N-tert-butyl- 4 acrylamide, acrylonitrile, hexahydro-l,3,5-triacrylo-s-triazine. In addition allyl derivatives are suitable cross linking monomers. Suitable examples include: diallyl phthalate, diallyl fumarate, allyl diglycol carbonate, and triallyl cyanurate. The resultant solution is then cooled to room temperature. As the solution cools, it solidies, and the solid `solution can be then ground or broken up into pellets. The amount of this monomer may vary. However, at least l0-20% of monomer (by total weight of the resin) must be used to afford a sufficient amount for the subsequent copolymerization or curing of the resin. Greater amounts, however, up to about 60% can be used and are economically attractive to use. However, amounts of monomer above about 60% result in a mixture of solid and liquid. Therefore, use of greater than 60% monomer is not contemplated by the present invention 'which seeks to produce a solid polyester resin. As will be more clearly illustrated in the examples, some formulations cannot contain as much monomer as can others. The above amount of monomer is, therefore, to be considered as a guideline. In many cases, monomer amounts above 50% are not desirable because ya hi-gher amount will result in a solid-liquid mixture. No such considerations of liquids versus solids are normally encountered in the prior art because the prior art polyester monomer mixtures are liquids at room temperature when even only l0-20% monomer is used (the minimum considered necessary to effect adequate copolymerization). However, since the novel polyester resin of the invention provides solid resin which may be used in applications not previously contemplated or feasible for liquid polyester resins, the use of lesser amounts of monomer in certain formulations, so as to obtain a solid resin, is preferred.

The solid resins may have fillers blended in such as calcium carbonate, or talc. Coloring agents such as the iron oxides may also optionally be blended in. Other additives such as re-retardants also can be incorporated into the resin, particularly if they are solids which can be ground up and physically dispersed into the powdered mixture. Examples of such fire-retardant additives are the combination of hexachlorophene and antimony oxide. Reinforcing materials such .as glass fibers can also be blended with the 'solid resin.

The subsequent copolymerization or curing of the polyester resin is usually initiated by a free-radical generating catalyst such. as, for example, a peroxide catalyst; although, other free-radical generating means such as, for example, UV light or radiation can also be used. Examples of such free-radical generating catalyst include benzoyl peroxide, cumene hydroperoxide, methyl ethyl ketone peroxide and the like. Other free-radical generating catalysts which can also be used include, for example, 2,2-azobisisobutyrontrile. Polymerization accelerators such as cobalt compounds or sulfur compounds e.g. cobalt-naphthenate may also be used. A secondary promoter such as dimethyl aniline may also be used in conjunction with the above catalyst.

Some of the above catalysts such as, for example, methyl ethyl ketone peroxide are active at room temperature while others such as, for example, benzoyl peroxide are not active at temperatures below about 60-70 C. Because the invention contemplates that heat can be used during the subsequent copolymerization to melt the solid polyester resin powder back. into a liquid, this temperature differential may well iniiuence the selection of the particular catalyst. If a high temperature catalyst, such as, for example, benzoyl peroxide is used, it could be ground up and' added to the powdered polyester resin mixture and the mixture shipped with the catalyst already incorporated therein. This is not the normal practice when liquid polyester resins are used because room temperature catalyst would elect the curing immediately and even high temperature catalyst if placed in the liquid polyester resin would initiate premature curing. Therefore, separate packaging of catalysts is usually the practice. With the novel polyester resin of the invention, such can be eliminated and the catalyst incorporated directly into the mixture thus providing one component system which can be directly charged into a mold press and, on application of heat to melt the powder, cured into a thermoset molded object.

Other non-conventional techniques can also be practiced with the solid resin having a dry solid catalyst physically mixed therewith. For example, the catalystcontaining polyester resin powder could be dispersed in a volatile solvent such as acetone or the like just prior to curing. The solvent 'action of the acetone would bring the resin and catalyst into reactive contact with one another to initiate the copolymerization. The exothermic heat of curing would then drive off the solvent. The solid polyester resin-dry catalyst physical mixture could also be mixed into a liquid polyester resin just prior to cure to provide a thioxotropic mixture. The dry catalyst upon being wetted out by the liquid polyester resin would then initiate cure of the entire resin mixture.

The invention will 'be more easily understood by referring to the following examples and the attached tiow sheet.

EXAMPLE I Into a reaction vessel, equipped with thermometer, stirrer, reux condenser, and inert gas inlet tubes was added 1 mole of 1,3-di(2-hydroxyethoxy)benzene, 1 mole of neopentyl glycol and 2 rnoles of maleic anhydride. The reaction mass was heated, with constant stirring, until a temperature of 220 C. was reached. The Water of esterication Was removed by a stream of nitrogen gas bubbling through the reactants in the reaction vessel. The heating was continued for 7 hours until an Iacid number of 13 was reached. Thereupon the hot resin was Cut with suicient styrene to provide a 50-50 weight percent solution. Upon cooling to room temperature, the resin solution was a white solid. This solid Iwas ground to a ne powder and mixed with 2% by weight of ground benzoyl peroxide catalyst. The mixture was charged to a mold cavity in a press and heated to 135 C. for l hour to cure the resin. The cured product was a hard, tough, clear casting slightly yellow in color.

EXAMPLE II To illustrate the diderence in result when other dihydric alcohols are used having similar, but not the indentical, structures to the 1,3- `and 1,4di(2hydroxyethoxy) benzenes a number of polyesters were prepared by esterifying l mole of dihydric alcohol with l mole of maleic anhydride under the conditions described in Example I. In each case, the polyester was esteriiied to an acid number below 50. Each polyester was then dissolved into styrene to a 70% by weight polymer, 30% monomer weight ratio. After allowing the mixtures to cool to room temperature, each -was examined. 'I'he results are tabulated below.

TABLE I Physical state of the polyester resin Dihydric alcohol in polyester: at room temperature l,3-di(2hydroxyethoxy)benzene Soli-d 1,4-di(2-hydroxyethoxy)benzene Solid 1,2-di(2hydroxyethoxy)benzene Liquid 2,2di(4hydroxyethoxy phenyl) propane (bishydroxy ethyl ether of bis-phenol A) Liquid The results show the dilference when other dihydric alcohols are substituted for those of the invention.

EXAMPLE III Following the esteriiication procedure of Example I, a number of polyesters were prepared. Portions of the first, a propylene glycol-maleic anhydride unsaturated polyester condensed in 1:1 mole ratio were hot blended respectively in various weight ratios with each of the other unsaturated polyesters. Each of the other unsaturated polyesters comprised a ratio of 2 moles of l,3-di(2 hydroxyethoxy)benzene to 1 mole of maleic anhydride and 1 mole of a second dicarboxyl acid. Portions of each of these polyester blends were then diluted respectively with sufcient styrene to form 70:30, 60:40, and 50:50 poylester to monomer weight ratios. The physical state of each solution at room temperature is tabulated below:

TABLE IIA [Second polyester: 1,3-di(2hydroxyethoxy)benzene maleic anhydride, tetrahydrophthalie anhydride] Weight percent Weight percent of propylene Weight percent styrene glycol-maleic of second in polyester Physical state anhydride poiypolyester in resin (polyester of polyester ester in polyester polyester mixture plus resin at room mixture mixture monomer) temperature 30 Solid. 0 100 40 Do. 50 Do. 30 Do. 30 70 40 Do. 50 Do. 30 Do. 50 50 40 Do. 50 Do. 30 Do. 60 40 40 D0.

50 Liquid 30 Do. 70 30 40 D0. 50 Do.

TABLE IIB [Second polyester z 1,3.-d1 (2-hydroxyethoxy) benzene maleic anhydrlde, hexahydrothnlic anhydride] Weight percent Weight percent of propylene Weight percent styrene glycol-maleic of second in polyester Physical state anhydride polypolyester in resin (polyester of polyester ester in polyester polyester mixture plus resin at room mixture mixture monomer) temperature 30 Solid. 0 100 40 Do. l so De.

30 Do 30 70 40 Do. 50 Do. 30 Do. 50 50 40 Do. 50 Do. 30 Do. 60 40 40 Do. 50 Do. 30 Do. 70 30 40 Do. 50 Do.

TABLE IIC [Second polyester: 1,3-di(2hydroxyethoxy)benzene maleic anhydride, isophthalic acid] Weight percent Weight percent of propylene Weight percent of styrene glycol-maleic oi second in polyester Physical state anhydride polypolyester in resin (polyester of polyester ester in polyester polyester mixture plus resin at room mixture mixture monomer) temperature 30 Solid. 0 100 40 Do. 50 Do. 30 Do. 30 70 40 Do. 50 Do. 30 Do 50 50 40 Do 50 Do. 30 Liquid. 60 40 40 Do. 50 Do. 30 Do. 70 30 40 Do. 50 Do.

3,632,667 7 8 TABLE HD weight of styrene monomer. The physical state of each i i i l [Second polyester: 1,3-di(2hydroxyethoxy)benzene maleic anhydride, mixture at room temperatures are recorded as fol OWS terephthalic acid] Weight percent Weight percent of propylene Weight percent of styrene 5 glycol-maleic of second in polyester Physical state anhydride polypolyester in resin (polycslter of polytester TABLE IIIA. :itiiertihr'lepolyester piiyxetsie' mlIXntgnI-)ielilr tilpearaltilrle [Second Polyester: ethylene glycol maleic anhydride] Weight percent of Weight percent 100 Somljo 1 3di(2'hyd10XY of styrene in 50 D0 10 ethoxy) benzene Weight percent polyester resin Physical state 30 D0' malelc anhydride of second poly- (polyester mixof polyester 3 70 40 D0' polyester in ester in polyture plus resin at room 0 50 DOI polyester mixture ester mixture monomer) temperature d0 Do, 50 50 40 Do. 100 0 S011 11j0 50 Do. 50 DO' 6o 4o ig Limlri" 15 so DOI o '1)0. 70 30{ 40 Do. 30 Do. 0. 70 30 gg 113g' 50 50 4o Dgf 5o Liquid.

TABLE IIE [Second Polyester: 1,3-di(2hydr.oxyethoxy)benzene malcic anhydride, TABLE IHB Dhthalio anhydride] 2g [Second Polyester: diethylene glycol maleie anhydride] Weight percent Welght Percent Weight percent of Weight percent of propylene Weight percent of styrene t t 1, 3-di(2hydroxy 0f styrene in glycol-131610 0f Second in polyester Physical s a e ethoxy) benzene Weight percent polyester resin Physical state anhydride polypolyester in resin (polyester of polyester mame anhydride of Second p01y (polyester mix of polyester ester in polyester polyester mixture plus resin at room polyester in ester in p01y ture plus resin at mom mixture mixture monomer) temperature polyester mixture ester mixture monomer) temperature 3o soiid. 30 30 Solid 0 100 40 DO- 100 0 40 Da 50 D0* 5o D0. D0 3o D0. so 70 40 DO- 7o 3o 4o D0. 50 D0' 5o Do. 30 D0' 3o Do. 50 50 gg lgg 35 50 50 4o D0, 30 1130. 50 Liquid 40 O. 60 l 5o Do.

30 D 70 30 go Liquid 40 TABLE nic [Second polyester: propylene glycol maleic anhydride] Weight percent of Weight percent 1,3-di(2hydi'oxy of styrene in TABLE IIF ethixy) beliliziried ieight iercelnt (pollyestter resin Pfhyslical state y ma eic an y i e o secon po ypo yes er mi'xo o ester [Second polyester: 1,3-di(2-hydroxyethoxy)benzene malcic anhydride, 4D polyester in ester in p01y ture plus resign t room itaoonic anhydrlde] polyester mixture ester mixture monomer) temperature Weight percent Weight percent 30 Soni of propylene Weight percent of styrene 100 0 40 D Q glyeol-maleic of second in polyester Physical state D0. anhydride polypolyester in resin (polyester of polyester 30 D0. ester in polyester polyester' mixture plus YSSIH et room 5() 7o 3o 4o D0. mixture mixture monomer) temperature 50 D0. 30 D0. 30 sohd' 50 50 40 D0' 0 100 40 D0. 50 Da 50 D0 3o D0. 30 DO- 4o 6o 4o D0.- 30 70 40 DO- r 50 DO. 5o Do. o5 3o Do. 50 gg' 20 80 4o D0.- 50 u 50 D0: 50 Do.

30 Do. 40 4o Do Liqid l 0 o. 3o 40 Do. 60

50 D0. TABLE IIID [Second polyester: dip-ropylene glycol maleic anhydride] Weight percent of Weight percent lisrdmilydroxy- W iit t lifsttenem Ph i i t fet oxy enzene eig percen po yes er resin ysica s a e EXAMPLE 1V 60 malelc anhydride of second poly- (polyester mixof polyester polyester ln ester inpolyture plus resin at room Following the procedures of Example I, a number of Polyester mlxtufe @Ster nurture monomer) temperature polyesters were prepared using various dihydric alcohols. 30 50ML In each case, the dihydric alcohols were esteried with an 100 0 gg gg: equimolar amount of maleic anhydride. One `of the poly- 70 30 D0 esters so prepared was the esteriication product of maleio 70 30 g8 13g: anhydride and 1,3-di(2hydroxyethoxy)benzene. Portions 30 D05 of this polyster were hot blended respectively with varying 50 50 gg amounts by weight of each of the other polyesters and 4o 6o so Liquid.

then each mixture was diluted with varying amounts by TABLE 1HE [Second polyester 2 '1,3-butyl'ene glycol maleic anhydride] Weight percent of Weight percent 1, 3di(2-hyd.roxy oi styrene in ethoxy) benzene Weight percent polyester resin Physical state maleic anhydride of second poly- (polyester mixof polyester polyester in ester in polyture plus resin at room polyester mixture ester mixture monomer) temperature 30 Solid. 100 0 40 Do.

30 Do. 70 30 40 Do.

30 Do. 5 0 50 40 Do.

50 Liquid TABLE IHF [Second polyester: neopentyl glycol maleic anhydride] Weight percent of Weight percent 1, 3dl(2hydroxy of styrene in ethoxy) benzene Weight percent polyester resin Physical state maleic anhydride of second poly- (polyester mixof polyester polyester in ester in polyture plus resin at room polyester mixture ester mixture monomer) temperature 30 Solid. 100 0 40 Do. 50 Do. 30 Do. 70 30 40 Do. 50 Do. 30 Do. 50 50 40 Do.

50 Liquid TABLE IIIG [Second polyester: l,4cyclohexane dimethanol glycol maleic anhydride] Weight percent of Weight percent 1, 3di(2hydroxyoi styrene in ethoxy) benzene Weight percent polyester resin Physical state maleic anhydride oi second poly- (polyester mixof polyester polyester in ester in polyture plus resin at room polyester mixture ester mixture monomer) temperature 30 Solid. 100 0 40 Do. 50 Do. 30 Do. 70 30 40 Do. 50 Do. 30 Do. 50 50 40 Do. 50 Liquid.

EXAMPLE V TAB LE IV Percent Physical Methyl appearance at methac- Diallyl room Polyester Styrene rylate phthalate temperature 1 49 2l 30 0 Off-white, solid. 2- 49 21 0 30 Do.

Thus, the invention provides an unsaturated polyester resin which is a solid at room temperature. The solid unsaturated polyester resin can be ground into iine partioles to provide a molding powder which can be used for molding articles in a molding press or the like. The novel solid polyester resin when ground into line particles, can be physically mixed with dry catalyst powder Ito form a onepackage mixture which will readily cure upon application of heat to melt the powder. Thus, the novel polyester resin of the invention can be utilized in applications where the previous liquid unsaturated polyester resin could not be used.

What is claimed is:

1. An unsaturated polyester resin which is a solid, freeiiowing powder at room temperature comprising a solid solution of (a) 20 to 60% by total weight of monomer and polymer of an 8-ethylenically unsaturated monomer; and by difference (b) 40 to 80% rby total weight of monomer and polymer of a condensation polymer formed by estcrifying approximately stoichiometric amounts of:

(i) a dihydric alcohol, at least 15 moles percent (based on total moles of dihydric alcohol) which is a dihydroxy ether selected from the group consisting of l,3di(2hydroxyethoxy) `benzene and 1,4-di(2hydroxyetlroxy)benzene; with (ii) a dicarboxylic acid or anhydride at least 25 mole percent (based on total moles of dicarboxylic acid) of which is an ethylenically unsaturated dicarboxylic acid or anhydride.

2. The polyester resin of claim 1 wherein the unsaturated dicarboxylic acids are selected from the group consisting of maleic acid, maleic anhydride and fumarie acid.

3. The polyester resin of claim 1 wherein the dihydric alcohols consist essentially of a mixture of propylene glycol and 1,3-di(2hydroxyethoxy)benzene and the dicarboxylic acids consist essentially of an unsaturated dicarboxylic acid selected from the group consisting of maleic anhydride, maleic acid, fumaric acid, and itaconic acid and a second dicarboxylic acid selected from the group consisting of tetrahydrophthalic acid, hexahydrophthalic acid, isophthalic acid, terephthalic acid and phthalic acid, as well as their anhydrides.

4. The polyester resin of claim 1 wherein the dicarboxylic acid is selected from the group consisting of maleic acid, maleic anhydride, and fumaric acid; the dihydroxy ether 4is l,3di(2hydroxyethoxy)benzene and the remainder of the dihydric alcohol is selected from the group consisting of ethylene glycol; diethylene glycol; propylene glycol; dipropylene glycol; 1,3-butylene glycol; neopentyl glycol; and 1,4-cyclohexane dimethanol.

5. The polyester resin of claim 1 wherein the aethylenically unsaturated monomer is selected from the group consisting of styrene, alpha-methyl styrene, vinyl toluene, divinyl benzene, chlorostyrene, methyl methacrylate, diallyl phthalate, and mixtures thereof.

References Cited UNITED STATES PATENTS 2,456,318 12/ 1948 Ramler 260-83 2,686,164 8/1954 Arvin et al. 260-22 2,762,789 9/1956 Wotherspoon et al. 260-75 2,973,339 2/1961 Muenster et al. 260-47 OTHER REFERENCES Caldwell: Appn Ser. No. 26,927, Abstract in 664 O G. 958 (1952).

Vinogradova et al.: Vysokomol. Soedin., Ser. A 9, 2152-60 (October 1967). (Polymer Ser. U.S.S.R. 2432-42, Chem. Abstr. supplied.)

Stanley: Modern Plastics, 25 (12), 103 (1948).

Lawrence: Polyester Resins, Reinhold, New York, 1960 (pp. 24-27 and 88).

yBoenig: Unsaturated IPolyesters, Elsevier, New York, 1964 (pp. 6 and 166).

zParkyn et al.: Polyesters, vol. 2, Elsevier, New York, 1967 (p. 32).

-Bjorkstem yPolyesters, Reinhold, New York, 1956 (pp. and 167).

MELVIN GOLDSTEIN, |Primary Examiner' U.S. Cl. X.\R. 

